The following description is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art to the present technology.
A variety of food-borne illnesses are caused by bacterial pathogens. Common food pathogens include, for example, Campylobacter jejuni, Escherichia coli, Salmonella, Listeria monocytogenes, Shigella, Yersinia, Staphylococcus, Clostridium, Vibrio, and Bacillus cereus. Most food pathogens are Gram-positive bacteria which cause a variety diseases and ailments including meningitis (Listeria, Enterococcus, and Streptococcus); botulism (Clostridium), tetanus (Clostridium), gas gangrene (Clostridium), membranous colitis (Clostridium); urinary tract infections (Enterococcus), bacteremia (Enterococcus), bacterial endocarditis (Enterococcus), Sialadenitis, i.e., food poisoning (Staphylococcus); strep throat (Streptococcus), bacterial pneumonia (Streptococcus); anthrax (Bacillus), gastroenteritis (Bacillus); and diphtheria (Corynebacterium).
Pathogens, including food-borne pathogens, may be detected using a variety of biosensing techniques. Typically, biosensors rely on non-covalent binding of a pathogen's surface protein to an antibody to provide specificity. Such immunoassays may be limited, since they are only as effective as the non-covalent binding to the antibody. Typically, antibody binding is coupled with highly sensitive detection methods, such as electrochemical, surface plasmon resonance and piezoelectric-based methods. Alternatively, an enzyme-linked immunosorbent assay (ELISA) may be used to repeatedly cleave a fluorescent tag thereby amplifying the antibody binding event. While antibody binding can be strong, it is non-covalent. Further, a typical bacterial cell includes relatively few binding sites for a selective antibody. Moreover, existing antibody detection schemes react to their binding target regardless of whether the target is part of a live cell. Accordingly, such techniques are prone to false positives and increased background from dead cells and/or cell detritus. Consequently, even with sophisticated detectors, live food pathogen detection limits are still typically high, i.e., approximately 104 to 105 colony forming units per milliliter. Covalent pathogen detection methods that are rapid, sensitive, and specific to live cells, are of interest.